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Palladium

General
Name, Symbol, NumberPalladium, Pd, 46
Chemical series Transition metals
Group, Period, Block10[?], 5 , d
Density, Hardness 12023 kg/m3, 4.75
Appearance Silvery white metallic
Atomic Properties
Atomic weight 106.42 amu
Atomic radius (calc.) 140 (169) pm
Covalent radius 131 pm
van der Waals radius 163 pm
Electron configuration [Kr]4d10
e- 's per energy level2, 8, 18, 18, 0
Oxidation states (Oxide) 1 (mildly basic)
Crystal structure Cubic face centered
Physical Properties
State of matter Solid (__)
Melting point 1828.05 K (2830.82 F)
Boiling point 3236 K (5365 F)
Molar volume 8.56 ×10-3 m3/mol
Heat of vaporization 357 kJ/mol
Heat of fusion 17.6 kJ/mol
Vapor pressure 1.33 Pa at 1825 K
Speed of sound 3070 m/s at 293.15 K
Miscellaneous
Electronegativity 2.20 (Pauling scale)
Specific heat capacity 244 J/(kg*K)
Electrical conductivity 9.5 106/m ohm
Thermal conductivity 71.8 W/(m*K)
1st ionization potential 804.4 kJ/mol
2nd ionization potential 1870 kJ/mol
3rd ionization potential 3177 kJ/mol
Most Stable Isotopes
isoNAhalf-life DMDE MeVDP
102Pd1.02%Pd is stable with 56 neutrons
104Pd11.14%Pd is stable with 58 neutrons
105Pd22.33%Pd is stable with 59 neutrons
106Pd27.33%Pd is stable with 60 neutrons
107Pd{syn.}6.5 E6 y β-0.033107Ag
108Pd26.46%Pd is stable with 62 neutrons
110Pd11.72%Pd is stable with 64 neutrons
SI units & STP are used except where noted.
For alternate meanings, including traditional meanings much older than the one treated here, and some very recent software usage: See Palladium (disambiguation)

Palladium is a chemical element, in the periodic table that has the symbol Pd and atomic number 46. A rare sliver-white transition metal of the platinum group, palladium resembles platinum chemically and is extracted from some copper and nickel ores. It is primarily used as an industrial catalyst and in jewelry.

Table of contents

Notable Characteristics Palladium is a soft steel-white metal that resembles platinum, doesn't tarnish in air, and is the least dense and has the lowest melting point of the platinum group[?] metals. It is soft and ductile when annealed and greatly increases its strength and hardness when it is cold-worked. Palladium is chemically attacked by sulfuric and nitric acid but dissolves slowly in hydrochloric acid. This metal also does not react with oxygen at normal temperatures.

This metal has the uncommon ability to absorb up to 900 times its own volume of hydrogen at room temperatures. It is thought that this possibly forms Pd2H but it is not yet clear if this is a true chemical compound.

Common oxidation states of palladium are +2, +3 and +4. Recently, palladium compounds in which palladium has oxidation state +6 were synthesized. Applications When it is finely divided, palladium forms a good catalyst and is used to speed-up hydrogenation and dehydrogenation reactions and also used in petroleum refinery reactions. This metal is also alloyed and used in jewelry. Other uses;

History Palladium was discovered by William Hyde Wollaston in 1803. This element was named by Wollaston in 1804 after the asteroid Pallas, which was discovered two years earlier.

Wollaston found element 46 in crude platinum ore from South America. He did this by dissolving the ore in aqua regia, neutralizing the solution with sodium hydroxide, NaOH[?], precipitating platinum as ammonium chloroplatinate[?] through treatment with ammonium chloride[?], NH4Cl, then he added mercuric cyanide[?] to form the compound palladium cyanide[?]. Finally, he heated the resulting compound in order to extract palladium metal.

The compound palladium chloride[?] was at one time prescribed as a tuberculosis treatment at the rate of 0.065 g per day (approximately 1 mg per kg of body weight). This treatment did not have too many ill side effects but was later replaced by more effected drugs.

Derivation

Traditionally, a palladium is a statue of Pallas Athena, especially, the one that Odysseus took from the citadel of Troy and upon which the city's security was believed to depend. The word is a Latinization of the Greek παλλαδιον, which can be transliterated as "palladion". Occurrence Palladium is found as a free metal and alloyed with platinum and gold with platinum group metals in placer[?] deposits of the Ural Mountains, Australia, Ethiopia, South and North America. However it is commercially produced from nickel-copper deposits found in South Africa and Ontario (the huge volume of ore processed makes this extraction profitable in spite of its low concention in these ores). Isotopes Naturally occurring palladium is composed of six isotopes. The most stable radioisotopes are Pd-107 with a half-life of 6.5 million years, Pd-103 with a half-life of 17 days, and Pd-100 with a half-life of 3.63 days. Eighteen other radioisotopes have been characterized with atomic weights ranging from 92.936 amu (Pd-93) to 119.924 amu (Pd-120). Most of these have half-lifes that are less than a half an hour except Pd-101 (half-life: 8.47 hours), Pd-109 (half-life: 13.7 hours), and Pd-112 (half-life: 21 hours).

The primary decay mode before the most abundant stable isotope, Pd-106, is electron capture and the primary mode after is beta decay. The primary decay product before Pd-106 is rhodium and the primary product after is silver.

Radiogenic Ag-107 is a decay product of Pd-107 and was first discovered in the Santa Clara, California meteorite of 1978. The discoverers suggest that the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. Pd-107 versus Ag correlations observed in bodies, which have clearly been melted since accretion of the solar system, must reflect the presence of live short-lived nuclides in the early solar system.

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